The present invention relates to electrographic apparatus wherein toner particles removed from a photoconductor during a cleaning operation can be selectively returned to a development station for reuse or delivered to a container for disposal.
During operation of known electrographic apparatus a latent image is formed on a photoconductor, a development station provides particles of toner to the photoconductor for developing the latent image, and after the image is transferred to a copy sheet or the like, a cleaning station removes residual particles of used toner from the photoconductor. In some instances the toner particles removed at the cleaning station are returned to the development station for reuse. Apparatus for recycling used toner is disclosed, for example, in U.S. Pat. Nos. 3,660,863, 3,700,328, and 4,571,071, and in Item 17738 on page 37 of the January, 1979 edition of Research Disclosure, published by Kenneth Mason Publications Ltd., The Old Harbourmaster's, 8 North Street, Emsworth, Hampshire, P010 7DD, England. In the beforementioned U.S. Pat. No. 4,571,071, the recycling apparatus is disclosed for a color copier which is capable of applying toners of four different colors from four development stations to a photoconductor and recycling particles of each color toner back to the respective development station.
It also is known to remove residual toner particles from a photoconductor and deliver them to a container instead of recycling them. In this regard, see U.S. Pat. No. 4,082,061, for example. In the latter patent residual particles of toners of three different colors are removed from a photoconductor and delivered to three different collection bottles or containers.
In order to provide copies of a single color other than black, electrographic apparatus having a single development station that normally provides black toner particles to a photoconductor can be replaced with a similar development station having toner particles of a different color, for example red, green, blue, brown, etc. Developer particles of colors other than black can be used to print single color images on copy sheets, or can be used as an accent color on copy sheets on which black images also are produced during another run through the electrographic apparatus. If the electrographic apparatus has a system for recycling previously used toner particles removed at the cleaning station, then the recycling apparatus can contaminate the development stations by recycling some of the toner of one color (e.g. black) into a development station containing toner of a different color (e.g. red). At the same time, since the electrographic apparatus probably will be used primarily for producing black images, it is desirable to continue to recycle used black toner particles to the development station during long runs when black toner is being used.